Screens are employed in completions to retain solids produced with the desired hydrocarbons. There are many styles for such screens but a popular design is commonly known as a wire wrap screen. The design of such a screen involves using a perforated base pipe and securing axially oriented mounting rods to the exterior of the base pipe. The wire is then helically wrapped over the mounting rods and secured to them at each intersection. The spacing between adjacent windings determines the particle size that is allowed to get through the screen. Sometimes punched openings are provided in outer jackets that cover over the wire wrap to protect the screen during running in.
Many optimizations of the performance of such screens have been attempted in the past. Some of these have focused on the cross-sectional shape of the wire with an eye toward keeping the manufacturing process reliable while attempting to control the flow direction for the stated purposes of enhancing throughput or reliability of operation. One issue that affects such screens is the potential for erosion from high velocity fluids that entrain produced solids. Some designs take a triangular cross-section for the wrapped wire and overlay exterior filtering layers for protection as in U.S. Pat. No. 8,701,757. Another design illustrated in US 20100258300 uses a round section for the wrap wire and varying spacing between the windings along the length of the screen. WO 2010143060 shows triangular or near trapezoidal shapes for wire cross-section with the near trapezoidal formed from taking a triangular shape and trimming one of the angles back to an arc shape. Also of interest regarding the above-mentioned wire cross-sectional shapes are the following references: US 2013/0092391 (note paragraph 36 noting that the wire shape can control flux in the screen); US 2010/0224359 (triangular with a rounded corner or trapezoidal); U.S. Pat. No. 7,188,687 (keystone shaped cross-section); U.S. Pat. No. 8,267,169 (FIGS. 3 and 4 showing triangular with rounded outer face or diamond or arrowhead shapes for the wire section); U.S. Pat. No. 8,291,971 (triangular); US 2014/0158295 (triangular with outer surface coating in FIG. 14B); U.S. Pat. No. 8,267,169 (triangular with rounded outer surface in FIG. 8); US 2005/0082060 (triangular in FIG. 7) and U.S. Pat. No. 7,273,106 (triangular in FIG. 11).
What is common to all these designs is that regardless of the shape employed for the wire cross-section, there is but a single gap between windings such that when erosion enlarges this gap the larger particles will get through and the base pipe underneath will also be exposed to erosive effects of high velocity fluids with entrained solids. The present invention seeks to improve the existing designs by offering the spacing that defines the size of the particles screened out in duplicate so that the sizing capability for excluded solids remains if one of the spacings is enlarged by erosive effects. Furthermore the backup spacing is further protected from erosive effects of high velocity fluids by virtue of the enclosed circumferential space between the outer and inner gaps because the enlarged volume between the inner and outer gaps reduces fluid velocity by the turbulence that is created to further protect the inner gap of the wire wrap and add longevity to the screen in subterranean environments. The enlarged volume area can be geometrically designed to move the erosion from the primary or secondary gap to an inner sacrificial area that does not compromise sand control. These and other aspects of the present invention will be more readily understood by those skilled in the art from a review of the detailed description and the associated drawings while recognizing that the full scope of the invention is to be determined by the appended claims.